The computer-averaged Ganzfeld electroretinogram of patients with chronic schizophrenia off-medication (neuroleptics) demonstrates an increased implicit time of the cone a-wave when compared with a normal population. In addition, the first oscillatory potential has an increased implicit time. These findings suggest that both photoreceptor function and the function of cells within the outer and inner nuclear layers are sensitive to the influence of a dopamine blocker, implying a modulatory role for retinal dopamine in the response of the retina to light.